Concrete ship.



A4 MACDONALD.

CONCRETE SHIP.

APPLICATION FILED OCT.23, 1917.

Patented May 28, 1918.

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ATTORNEYS,

A. MACDONALD.

CONCRETE SHIP.

APPLICATION FILED OCT. 23, 1917.

1,267,680. Patented May 28, 1918.

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WITNESS: INVENTOR.

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ED STATES PATENT one .ALAN MACDONALD, OESAN Fnenorsoo, cALIron'NIA,AsSIGNon T0 SAN FRANCISCO SHIP BUILDING (30., ,OF FRANCISCO, CALIFORNIA,A CORPORATION OF CALI- FOBNIA.

CONCRETE SHIP.

Specification of Letters Patent.

Patented May as, 1918.

Application filed October 23, 1917.- Serial No. 198,010.

To all whom it may concern:

Be it known that I, Aux MACDONALD, a citizen of the United States,residing at the city and county of San Francisco and State ofCalifornia, have invented certain new and useful Improvements inConcrete Ships, of which the following is a specification.-

My invention relates to the art of .ship building and especially toconcrete-ships. One of the main diificulties in building a concrete shipis to keep the structure within the required weight. The solution restslargely in keeping the walls and bottom thin.

Considering the whole ship as a large box girder, spanning two waves, oron the top of one wave, with bow and stern out of the water, bad bendingand shearing stresses are produced in the sides and bottom. Due to thenecessity of keeping the walls thin, by a small area of concrete, it isnecessary to add steel to take care of this shear.

It is customary in concrete walls of buildings and other structureswhere thin walls are used, to put steel bars at right angles to oneanother, vertically and horizontally, to resist the temperaturestresses. In the walls of a ship, however, if the bars are placedvertically and horizontally, while they will resist stress to someextent, they are nevertheless insuflicient to resist the shearingstress, which acting at an angle of 45 degrees to the vertical, wouldrequire said bars, when so disposed, to be unduly large, and, in turn,such large bars would require a greater thickness of concrete wall tohold them, thus materially increasing the dead weight of the structure.

In order, therefore, to reduce this thickness of wall and to save bothsteel and concrete, my invention consists primarily in the dispositionof the bars in approximate alinement with the direction of the resultantshearing stress, said disposition being oblique to the vertical andhorizontal, the preferred inclination thereto being 45 degrees.

Furthermore, considering a ship under a hogging or sagging strain, theentire structure is in fiexure and is so designed. WVhen sagging, thedeck is in compression and the bottom in tension, just as any other formof beam under similar circumstances. Under these conditions, and since aship is hollow inside, the tensional stresses in the bottom aretransmitted to theside at the knuckle,

connections, to resist them.

that is, the junction of the bottom and side,

very great, and it has been the custom in concrete ships to increase thesize of the sides and the bottom and deck slabs, at these Theseconnections, therefore, become very heavy.

To save this weight and to increase the efliciency of the construction,my invention further contemplates the continuation of the obliquelydisposed bars into the deck and bottom slabs to a distance far enoughfor the adhesion of the cement to develop their strength, thecontinuation or extension of the bars being oblique to the center lineof the ship so as to be exactly in. line of the stress. Lastly, it isbest to terminate said bars in the deck and bottom along difi'erentlines.

Referring to the accompanying drawings,

Figure 1 is a perspective view, broken, of a concrete ship showing myimprovement.

Fig. 2 is a plan view, broken, of the deck, showing the steel barsexposed.

Fig. 3 is a cross sectional view of the ship.

1 is the side, 2 is the bottom and 3 is the deck of a ship. These are ofconcrete, as indicated. In the concrete sides of the ship are embeddedthe steel bars 4 and 5, in such number as may be predetermined. The barsare disposed diagonally, those designated by -l extending in onedirection and those marked 5 extending in the opposite direction, thebars thus crossing each other. Their best angle is approximately one ofl5 degrees to the vertical, thereby lying in line with the direction ofshearing stresses. The bars are continued 01' extended at 4. and 5,respectively, into the bottom, and at l and 5 into the deck, theseextensions lying obliquely to the fore and aft median line of the ship,the angle being best 45 degrees.

In order to avoid the termination of these extensions along the sameline, it is best to carry alternate ones into the bottom and deck slabsfarther in. This is easily done by having all the bars of the samelength and extending the lower ends of alternate ones into the bottom toa greater distance than their upper ends are extended into the deck, andvice versa. This is shown clearly in Figs. 1 and 2, and it has theadvantage of keeping the full strength of all the bars at the knuckleand gunwaie, where it is needed, and leducing the strength toward the median fore and aft line, Where the stresses are not so great.

I claim 1. In a concrete ship, the concrete side Walls thereof havingembedded Within them a plurality of obliquely disposed metallic barscrossing each other, and the concrete deck and concrete bottom of saidship having embedded in them continuotions of said bars disposedobiiqueiy to the fore and aft center line ofthe ship.

2.111 a concrete ship, the concrete sides, bottom and deck thereofhaving embedded Copies of this patent may be obtained for five centseach, by addressing the Within them a plurality of obliquely disposedbars crossing each other in the sides, and continued obliquely inrthebottom and deck, the extremities of alternatecbars terminating in saidbottom and deck along different lines.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing Witnesses.

ALAN liiACDONALD.

Witnesses:

WM. F. BOOTH, D. B. RICHARDS.

Commissioner of .Patents "Washington, D. U.

